1. Field of Invention
The present invention relates to a driving circuit. More particularly, the present invention relates to a light-emitting diode (LED) driving circuit.
2. Description of Related Art
Generally, a light-emitting diode (LED) driving circuit, provided for display applications, converts an input voltage into an output voltage required to drive one or several connected light-emitting diodes. The brightness of the light-emitting diodes can vary when using the pulse width modulation (PWM) dimming method.
However, when the PWM dimming method is applied, ripples are generated in the output voltage of the light-emitting diode driving circuit. In addition, a diode current flowing through the light-emitting diodes varies according to the PWM dimming method and also causes the ripples, so a closed-loop transfer function of the light-emitting diode driving circuit is affected by the ripples and cannot be changed quickly. Moreover, the closed-loop transfer function is also affected by a slew rate of an error amplifier that is often employed in the light-emitting diode driving circuit, such that the voltage of a compensating capacitor cannot be changed quickly enough to reduce the ripples. Therefore, the ripples of the output voltage cannot be minimized and the light-emitting diode driving circuit cannot be stably operated.